Gram positive

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 The Gram-positive bacterial cell wall is one of the two types of bacterial cell walls the other being Gram-negative cell walls. The Gram-positive cell walls are mainly composed of peptidoglycan although they also consist of surface proteins, teichoic and lipoteichoic acids the latter of which connects the cell wall to the cell membrane. The teichoic and lipoteichoic acids contribute to the positive charge of the bacterial cell surface and they are glycerophosphate or ribitol phosphate- containing acidic polysaccharides. 

The thick layer of peptidoglycan enables the cell wall retain the purple colour of crystal violet upon constriction consequent upon treatment with iodine. Thus Gram-positive bacterial cell walls stain pruple.

Examples of Gram-positive bacteria include Staphylococcus aureus, Streptococcus pyogenes and Streptococcus pneumonia amongst others.

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